1. Field of Invention
The present invention relates in general to a twin clutch transmission in which speed gearings are parted into two groups which are selectively operated by respective automatic clutches, and more particularly to a gear hit noise suppression system for use in such twin clutch transmission.
2. Description of Related Art
Hitherto, various types of twin clutch transmissions have been proposed and put into practical use particularly in the field of wheeled motor vehicles. As is known, the twin clutch transmissions are of a type in which gears are parted into two groups each having an automatic clutch, so that operative condition of each group of gears is carried out by selectively engaging the corresponding automatic clutch. Some of the transmissions of this type are disclosed in Laid-Open Japanese Patent Applications 8-320054, 9-196164, 10-89457, 11-37260, 11-82729, 11-201271 and 2001-295898.
However, due to inherent constructions, the transmissions of these publications have failed to sufficiently suppress or damp gear noises produced by the gears used in the transmission. Particularly, in the transmission of the publication 8-320054, there is employed an arrangement in which when one group of gears actually work for power transmission having the corresponding clutch engaged, the other group of gears are caused to assume a neutral condition having the corresponding clutch kept engaged. In this arrangement, even in the neutral condition, the gears of the other group are forced to input the engine rotation because of the engaged condition of the corresponding clutch. Accordingly, when the input section of the transmission undergoes a speed change, a so-called gear hit noise is produced due to a back rush phenomenon that is inevitably produced by mutually engaged gears of the other group in a rest condition.
It is therefore an object of the present invention to provide a twin clutch transmission which is suppressed from producing a gear hit noise which would be caused by back rush phenomenon of the gears of one group that is in a rest condition.
According to a first aspect of the present invention, there is provided a twin clutch transmission for use with a prime mover, which comprises a first group of gears which are operable to select one of a first group of speed gearings with the aid of a first selection mechanism; a second group of gears which are operable to select one of a second group of speed gearings with the aid of a second selection mechanism; a first automatic clutch which is incorporated with the first group of gears to establish the selected one of the first group of gearings when engaged; a second automatic clutch which is incorporated with the second group of gears to establish the selected one of the second group of gearings when engaged; and a control unit which controls the first and second selection mechanisms and the first and second automatic clutches, the control unit being configured to carry out establishing a condition wherein both the first and second automatic clutches are in their engaged conditions and wherein one of the first and second groups of gears is operated to select a certain speed gearing with the aid of the corresponding selection mechanism while leaving the other of the first and second groups of gears in a neutral condition with the aid of the corresponding selection mechanism; and releasing the engaged condition of the automatic clutch incorporated with the other of the first and second groups of gears when the other of the first and second groups of gears is in a critical condition to induce a gear hit noise.
According to a second aspect of the present invention, there is provided a method of controlling a twin clutch transmission for use with a prime mover, the transmission including a first group of gears which are operable to select one of a first group of speed gearings with the aid of a first selection mechanism; a second group of gears which are operable to select one of a second group of speed gearings with the aid of a second selection mechanism; a first automatic clutch which is incorporated with the first group of gears to establish the selected one of the first group of gearings when engaged; and a second automatic clutch which is incorporated with the second group of gears to establish the selected one of the second group of gearings when engaged, the method comprising establishing a condition wherein both the first and second automatic clutches are in their engaged conditions and wherein one of the first and second groups of gears is operated to select a certain speed gearing with the aid of the corresponding selection mechanism while leaving the other of the first and second groups of gears in a neutral condition with the aid of the corresponding selection mechanism; and releasing the engaged condition of the automatic clutch incorporated with the other of the first and second groups of gears when the other of the first and second groups of gears is in a critical condition to induce a gear hit noise.